In September 2007, two separate incidents of similar landing gear failures occurred within four days of each other on BombardierDash 8-Q400 aircraft, both operated by Scandinavian Airlines (SAS). A third incident, again with an SAS aircraft, occurred in October 2007, leading to the withdrawal of the type from the airline's fleet.
Prior to landing, the right main landing gear failed to lock and the crew circled for an hour before attempting a prepared emergency landing. Upon touchdown, the right landing gear collapsed, the right wing touched ground, and a fire broke out. The fire went out before the aircraft came to rest and all passengers and crew were evacuated. Five people suffered minor injuries, some from propeller parts entering the cabin and others from the evacuation.
When the handle for lowering the landing gear was activated, the indicator showed two green and one red light. The red light indicated that the right main gear was not locked in position. The landing was aborted. Attempts at lowering the gear manually were also unsuccessful. Investigation into the cause of the failure to deploy revealed that the right main gear hydraulicsactuator top eyebolt was separated from the actuator. A further analysis of the actuator showed corrosion on the inside leading to reduced mechanical strength of the actuator and eventual failure.
On September 19, 2007, the prosecutor of Stockholm commenced a preliminary investigation regarding suspicion of creating danger to another person.
Scandinavian Airlines System (SAS) has been accused of cutting corners for maintenance. As the Swedish Civil Aviation Authority began an investigation of the accident, it brought renewed focus on SAS maintenance procedures. Only two weeks previously, Swedish authorities had levelled a scathing critique at the airline after an aircraft of the same model nearly crashed because its engine accelerated unexpectedly during landing. The airline reportedly made 2,300 flights in which safety equipment was not up to standard, although the airline has denied this.
Radio Sweden International reports that a security analyst for the Norwegian Civil Aviation Authority has sent a warning to other Scandinavian aviation bureaus concerning sub-standard SAS maintenance procedures, including one instance where an aircraft took off after the pilot reported a fuel leak. This warning, while publicized subsequent to the landing gear related accidents, was apparently written before them.
On October 27, 2007, a Dash 8-400 (LN-RDI), SAS flight SK2867 from Bergen, Norway, with 40 passengers and 4 crew members was en route to Copenhagen, Denmark, when problems with the main landing gear were discovered. After waiting about two hours in the air to burn fuel and troubleshoot, the pilots attempted a prepared emergency landing. The pilots were forced to land the aircraft with the right main landing gear up. The right engine was shut off for the landing, because in the previous landings the propeller had hit the ground and shards of it ripped into the fuselage. This was not on the emergency checklist, rather it was the pilots making a safety based decision. The aircraft stopped on the runway with the right wing touching the runway at 1653 local time. It did not catch fire and the passengers and the crew were evacuated quickly. There were no serious injuries. The aircraft in question was one of six that had been cleared to fly just a month before, following the grounding of the entire Scandinavian Airlines Dash 8-400 fleet due to similar landing gear issues. The entire fleet was grounded again following the incident.
The preliminary Danish investigation determined this latest Q400 incident is unrelated to the airline's earlier corrosion problems, in this particular case caused by a misplaced o-ring found blocking the orifice in the restrictor valve. Accordingly, EASA announced that "...the Scandinavian airworthiness authorities will reissue the Certificates of Airworthiness relevant to this aircraft type in the coming days".
After the third incident in Copenhagen, Scandinavian Airlines System (SAS) grounded their entire Dash-8-400 fleet consisting of 27 aircraft, and a few hours later the manufacturer Bombardier Aerospace recommended that all the Dash-8-400 aircraft with more than 10,000 flights stay grounded until further notice, affecting about 60 of the 160 Q400 aircraft used worldwide. As a result, several hundred flights were cancelled around the world. Horizon Airlines grounded 19 of their aircraft and Austrian Airlines grounded eight.
On September 13, 2007, Transport Canada issued an Airworthiness Directive applicable to Bombardier Q400 turboprop aircraft instructing all Q400 aircraft operators to conduct a general visual inspection of the left and right main landing gear system and main landing gear retract actuator jam nut. This effectively grounded all Q400 aircraft until the inspection had been carried out.
On September 14, 2007, Bombardier issued an All-Operators Message (AOM) recommending new procedures concerning the landing gear inspection for all aircraft with more than 8,000 flights. Bombardier acknowledged the likelihood of corrosion developing inside the retract actuator.
Previous maintenance procedures mandated checking this component after 15,000 landings. The new maintenance schedule affects about 85 of the 165 Q400 aircraft worldwide. Some operators have found that spare parts for this unexpected actuator replacement program are not available, grounding their aircraft indefinitely.
Skandinavisk Tilsynskontor investigators detected corrosion inside the actuator on 25 of 27 aircraft they checked. Accordingly, SAS decided to continue the grounding of its Dash-8-400 fleet until all the affected parts have been replaced.
On October 28, 2007, SAS announced that it will retire all Dash-8-Q400 aircraft.
On March 10, 2008, a multi-party agreement was announced, attempting to finalize the roles of maintenance and manufacture in causing the SAS incidents; as settlement the airline and its partners ordered a replacement set of short-haul planes from Bombardier, and in turn received a US $164 million discount.
It has been speculated that a November 2007 shakeup of Bombardier management has been spurred by the Dash-8-Q400 issues.
On 9 June 1995, Ansett New Zealand Flight 703 from Auckland Airport to Palmerston North crashed west of the Tararua Ranges and 16 km east of Palmerston North airport during an instrument approach in inclement weather. A landing gear failure distracted the pilot and co-pilot, failing to notice the aircraft had descended into danger. This was complicated by a ground proximity warning not sounding until immediately before the crash. Four people were killed and most other passengers injured. The official investigation by Air Transport regulators found that the pilot and co-pilot should have abandoned the approach and dealt with the gear failure before attempting a new approach.
On 28 January 2002, a wheel detached from the starboard side of the undercarriage at an aircraft owned by Tyrolean Airways while taxiing before takeoff from Frankfurt Airport. The missing wheel was detected by visual inspection of the aircraft after landing in Salzburg Airport, and the wheel was later recovered. A probable cause was a displaced outer bearing grease seal, causing overheating.
On 13 March 2007, All Nippon Airways Flight 1603, a Q400 nose-landed safely at Kōchi Ryōma Airport after the front wheel of the aircraft failed to deploy. Bombardier advised all operators to inspect the nose landing-gear mechanism of the aircraft. On November 11, it was reported that the Japanese Transport Ministry is preparing to blame Bombardier for improper assembly procedures, in this case forgetting a necessary bolt. In Japan, this incident was followed only a week later when a Dash-8-100 made an emergency landing at Kumamoto Airport after extending its gear manually. See also: All Nippon Airways Incidents.
On 20 April 2007, a Dash 8 operated by Bahamasair suffered a port side landing gear collapse on landing at Governor's Harbour Airport, Bahamas; no injuries were reported but inquiries continue. The aircraft suffered left wing and propeller damage, and was dismantled and shipped off-site.
On September 21, 2007, Lufthansa Flight LH4076 (tail number D-ADHA) with 68 passengers and four crew members was on flight to Florence, Italy when problems with the front landing gear were identified. The pilots were forced to make an emergency landing at Munich Airport. The aircraft landed with its front landing gear up. There were no injuries. The aircraft is owned by Augsburg Airways.
On 10 October 2007, a SAS Denmark Q400 headed for Poland returned to Copenhagen when the pilots got problems with the indicator lights of the front landing gear. The pilots got a yellow indication that the front landing gear hatch didn't close after taking off. Then they heard the hatch closing, then opening and closing again.
On 9 February 2011, an Air New Zealand Bombardier Q300 Dash 8 aircraft – Flight NZ8309, operated by the subsidiary Air Nelson again suffered a nose wheel failure upon landing at Blenheim Airport. It had been scheduled to fly from Hamilton to Wellington (in the North Island), but was diverted to Blenheim after crew reported a problem with the undercarriage. After circling the airport four times, the aircraft landed with the nose gear undeployed coming to a stop approximately two thirds along the length of the runway. No injuries were sustained. A Transport Accident Investigation Commission report (#11-002), found a faulty inhibit switch caused the loss of nosewheel steering on departure and was the cause of the landing gear later not extending normally. The pilots were unable to utilise the alternate extension system as they did not apply enough force to the release handle for the uplock (or possibly did not hold the release handle in position long enough for the uplock to disengage). This was found to be at least in part due to the flight simulators not requiring the full 40 kg (90 lbs) or more force as required in the actual aircraft. Image during landing here 
On 4 March 2011, a wheel fell off a Bombardier Q400 operating a Flybe flight from Exeter to Newcastle. The aircraft returned to Exeter and made an emergency landing, no one was injured. The AAIB report said the wheel bearing had seized and allowed the wheel to detach.
On 7 March 2011, an Air Iceland Bombardier Q100 Dash 8 aircraft suffered a collapsed right landing gear whilst landing at Nuuk Airport, Greenland. Several of the 31 Passengers on board reported a severe crosswind gust immediately prior to the main gear touching down, which resulted in the aircraft drifting over and subsequently making contact with snow banks alongside the runway, causing the right gear to collapse.
On 27 September 2013, Croatia Airlines Flight 464 from Zagreb to Zurich – Dash 8 Q-400 registration number 9A-CQC landed without nose wheel at Zurich Airport. The crew noted that nose gear was blocked and has failed to lock into the position during first landing attempt. After performing go-around and circling for the next 40 minutes in the holding pattern, they made a second landing attempt and landed safely on runway 14 at 18:18 GMT/UTC without nose wheel. There were no injuries among 60 passengers and 4 crewmembers, while the aircraft sustained no major damage.
On 6 November 2014, Jazz (airline), operating as Air Canada Express Flight 8481, from Calgary to Grande Prairie – Dash 8 Q-400 made an emergency landing at Edmonton International Airport. One of the main landing gear tires apparently blew on takeoff. Due to bad weather in Calgary, the pilot redirected to Edmonton. During landing in Edmonton, the right side main landing gear collapsed, injuring 3 people among 71 passengers and 4 crew members. The aircraft sustained damage, including a propeller penetrating the cabin, causing one of the injuries.
On 30 September 2015 a Luxair aircraft flying from Saarbruecken to Luxembourg experienced smoke in the cabin during the initial climb out phase and performed a belly landing on the runway. Nobody was hurt.
September 17, 2016: airBaltic flight BT641 using a Bombardier Q400 NextGen (registered YL-BAI) from Riga to Zurich made an emergency landing at Riga Airport without its nose landing gear deployed. There were no injuries among 63 passengers and 4 crewmembers.
On 23 February 2017: Flybe Flight 1284 using a Bombardier Q400 (registered G-JECP) from Edinburgh to Amsterdam made a landing at Amsterdam Airport Schiphol in windy conditions resulting in a right main gear collapse. No injuries have been reported and the aircraft sustained substantial damage.